I managed to work out the problem... Sort of.
My computer is a Macbook running Windows 10 using Apple bootcamp software. When transferring the APK by USB cable and Google drive upload, then download to phone, none of these methods work and result in the error as shown in the screenshot above
I opened my Capx on a Windows PC and rebuilt the APK, transferred to phone with USB cable and it works!
Same on my chromebook, built the APK and transferred using google drive to phone and that also works.
Ashley There must be a problem with building/compiling when using a Macbook running Windows. Hope this info is useful for ironing out bugs with Construct 3.